Here is one that is new to me, but perhaps not to you folks in the USA.
It is a 222 necked down to 20 cal, with an angle change on the shoulder but only a few degrees. Like the 204 it will work well with a variety of powders and bullet weights. More speed for less powder
I have a Lilja barrel in a 1-9 which may be a little fast for this build, but I may just give it a try on a seldom used Sako Vixen in 223.FS

Sounds like fun to me. Post pix and results when completed
Best
GWB

The 222 case necked to 20 cal with 30degree shoulder from Tod Kindlers book'" The Terific Twenties" is the 20 VarTarg Turbo.
I have the 20VarTarg on the 221 FB case
Check out the link for the 20 cal variations and the cases they are built on.
http://www.angelfire.com/sd/6m...y/twentycaliber.html

Von Gruff.

I built myself a 20x222. No other changes. It is an absolute ground hog "lightning bolt". Lilja bbl, 32gr Bal. Tip, 2015 powder. Easy to form, easy to load and you can see your hits, and misses, through the scope.

Then there's the Tactical 20 and the 20 Practical,
both using very readily available .223 brass.

20/222 is sometimes called a 20Sprinter here as sprinter made the barrels and did the chambering. Been around a surprisingly long time.
Cheers...
Con